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      speed for getting info from pipe and proc system
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        <h3 id="Test-code"><a href="#Test-code" class="headerlink" title="Test code"></a>Test code</h3><p>compile with <code>gcc -Wall -o test test.c</code></p>
<p>The include file time_test.h, can be got frome<br><a href="https://github.com/matrix207/C/blob/master/util/time_test.h" target="_blank" rel="external">https://github.com/matrix207/C/blob/master/util/time_test.h</a></p>
<pre><code>#include &lt;stdio.h&gt;  
#include &lt;stdlib.h&gt;  
#include &lt;string.h&gt;  
#include &lt;pthread.h&gt;
#include &lt;sys/types.h&gt;  
#include &lt;sys/stat.h&gt;  
#include &lt;fcntl.h&gt;  
#include &lt;unistd.h&gt;  
#include &lt;signal.h&gt;  
#include &lt;sys/socket.h&gt;
#include &lt;sys/wait.h&gt;
#include &lt;arpa/inet.h&gt;
#include &lt;netinet/in.h&gt;
#include &lt;net/if.h&gt;
#include &lt;sys/ioctl.h&gt;
#include &quot;time_test.h&quot;

int exec_cmd(const char *cmd, char *result, const int size)
{
    FILE *fp = NULL;

    if (cmd == NULL) {
        printf(&quot;cmd can not be NULL\n&quot;);
        return 1;
    }

    if (NULL == (fp = popen(cmd, &quot;r&quot;))) {
        fprintf(stdout, &quot;Fail to do %s\n&quot;, cmd);
        return 1;
    }

    memset(result, 0, size);
    printf(&quot;-------1-------\n&quot;);
    fgets(result, size, fp);
    printf(&quot;-------2-------\n&quot;);

    pclose(fp);
    return 0;
}

void get_from_proc(char *interface)
{
    int sockfd;
    struct ifreq ifr;
    char mac_addr[30]={0};

    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if( sockfd == -1) {
        perror(&quot;create socket falise...mac\n&quot;);
        return; 
    }

    memset(&amp;ifr,0,sizeof(ifr));
    strncpy(ifr.ifr_name, interface, sizeof(ifr.ifr_name)-1);

    if ((ioctl(sockfd, SIOCGIFHWADDR, &amp;ifr)) &lt; 0) {
        printf(&quot;mac ioctl error\n&quot;);
        return;
    }

    snprintf(mac_addr, sizeof(mac_addr), &quot;%02x%02x%02x%02x%02x%02x&quot;,  
            (unsigned char)ifr.ifr_hwaddr.sa_data[0],
            (unsigned char)ifr.ifr_hwaddr.sa_data[1],
            (unsigned char)ifr.ifr_hwaddr.sa_data[2],
            (unsigned char)ifr.ifr_hwaddr.sa_data[3],
            (unsigned char)ifr.ifr_hwaddr.sa_data[4],
            (unsigned char)ifr.ifr_hwaddr.sa_data[5]);

    printf(&quot;local mac:%s \n&quot;,mac_addr);

    char *address;
    struct sockaddr_in *addr;
    if (ioctl(sockfd,SIOCGIFADDR,&amp;ifr) == -1)
        perror(&quot;ioctl error&quot;),exit(1);
    addr = (struct sockaddr_in *)&amp;(ifr.ifr_addr);
    address = inet_ntoa(addr-&gt;sin_addr);
    printf(&quot;inet addr: %s \n&quot;,address);

    close(sockfd);
}

void get_from_pipe(char *interface)
{
    char cmd[100] = {0};
    /* char *format=&quot;ifconfig %s |grep %s |awk &apos;{print $5}&apos;&quot;; */
    char *format=&quot;ifconfig %s |grep ether |awk &apos;{print $2}&apos;&quot;;
    snprintf(cmd, sizeof(cmd), format, interface, interface); 
    char result[150] = {0};
    if (0 == exec_cmd(cmd, result, sizeof(result))) {
        printf(&quot;mac is %s\n&quot;, result);
    } else {
        printf(&quot;Fail\n&quot;);
    }
}

void time_test(int argc,char **argv)
{
    /* XXX: change this for your computer */
    char *interface = &quot;p4p1&quot;;
    if (argc == 2)
        interface = argv[1];

    TIME_START();
    printf(&quot;---------from proc system---------\n&quot;);
    get_from_proc(interface);
    TIME_END();

    TIME_START();
    printf(&quot;---------from pipe---------\n&quot;);
    get_from_pipe(interface);
    TIME_END();
}

int main(int argc,char **argv)
{
    time_test(argc, argv);
    return 0;
}
</code></pre><h3 id="Test-detail"><a href="#Test-detail" class="headerlink" title="Test detail"></a>Test detail</h3><p>Using strace to log system calling time (output to file 1.log)</p>
<p><code>strace -tT -o 1.log ./test</code></p>
<p>The log info we care list as below:</p>
<pre><code>11:00:47 write(1, &quot;---------from proc system-------&quot;..., 35) = 35 &lt;0.000030&gt;
11:00:47 socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 3 &lt;0.000049&gt;
11:00:47 ioctl(3, SIOCGIFHWADDR, {ifr_name=&quot;p4p1&quot;, ifr_hwaddr=00:23:ae:96:d6:9a}) = 0 &lt;0.000012&gt;
11:00:47 write(1, &quot;local mac:0023ae96d69a \n&quot;, 24) = 24 &lt;0.000018&gt;
11:00:47 ioctl(3, SIOCGIFADDR, {ifr_name=&quot;p4p1&quot;, ifr_addr={AF_INET, inet_addr(&quot;172.16.50.39&quot;)}}) = 0 &lt;0.000013&gt;
11:00:47 write(1, &quot;inet addr: 172.16.50.39 \n&quot;, 25) = 25 &lt;0.000021&gt;
11:00:47 close(3)                       = 0 &lt;0.000019&gt;
11:00:47 write(1, &quot;Elapsed time 471 usec\n&quot;, 22) = 22 &lt;0.000017&gt;
11:00:47 write(1, &quot;---------from pipe---------\n&quot;, 28) = 28 &lt;0.000018&gt;
11:00:47 brk(0)                         = 0x1af3000 &lt;0.000009&gt;
11:00:47 brk(0x1b14000)                 = 0x1b14000 &lt;0.000010&gt;
11:00:47 brk(0)                         = 0x1b14000 &lt;0.000007&gt;
11:00:47 pipe2([3, 4], O_CLOEXEC)       = 0 &lt;0.000014&gt;
11:00:47 clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7f6bff5eaa10) = 7658 &lt;0.000077&gt;
11:00:47 close(4)                       = 0 &lt;0.000008&gt;
11:00:47 fcntl(3, F_SETFD, 0)           = 0 &lt;0.000007&gt;
11:00:47 write(1, &quot;-------1-------\n&quot;, 16) = 16 &lt;0.000020&gt;
11:00:47 fstat(3, {st_mode=S_IFIFO|0600, st_size=0, ...}) = 0 &lt;0.001732&gt;
11:00:47 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f6bff603000 &lt;0.000016&gt;
11:00:47 read(3, &quot;00:23:ae:96:d6:9a\n&quot;, 4096) = 18 &lt;0.003692&gt;
11:00:47 write(1, &quot;-------2-------\n&quot;, 16) = 16 &lt;0.000170&gt;
11:00:47 close(3)                       = 0 &lt;0.000009&gt;
11:00:47 wait4(7658, [{WIFEXITED(s) &amp;&amp; WEXITSTATUS(s) == 0}], 0, NULL) = 7658 &lt;0.000043&gt;
11:00:47 --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=7658, si_status=0, si_utime=0, si_stime=0} ---
11:00:47 munmap(0x7f6bff603000, 4096)   = 0 &lt;0.000018&gt;
11:00:47 write(1, &quot;mac is 00:23:ae:96:d6:9a\n&quot;, 25) = 25 &lt;0.000018&gt;
11:00:47 write(1, &quot;\n&quot;, 1)              = 1 &lt;0.000014&gt;
11:00:47 write(1, &quot;Elapsed time 6639 usec\n&quot;, 23) = 23 &lt;0.000022&gt;
</code></pre><p>find the max 10 time by <code>awk &#39;{print $NF}&#39; 1.log |sort |tail</code></p>
<pre><code>&lt;0.000021&gt;
&lt;0.000022&gt;
&lt;0.000030&gt;
&lt;0.000043&gt;
&lt;0.000049&gt;
&lt;0.000077&gt;
&lt;0.000164&gt;
&lt;0.000170&gt;
&lt;0.001732&gt;
&lt;0.003692&gt;
</code></pre><p>then find the time killer <code>grep -E &quot;001732|003692&quot; 1.log</code></p>
<pre><code>11:00:47 fstat(3, {st_mode=S_IFIFO|0600, st_size=0, ...}) = 0 &lt;0.001732&gt;
11:00:47 read(3, &quot;00:23:ae:96:d6:9a\n&quot;, 4096) = 18 &lt;0.003692&gt;
</code></pre><p>so, we know that the killer code is </p>
<pre><code>fgets(result, size, fp);
</code></pre><p>If we using much code for our programming, and time is what we should care about,<br>then avoid pipe code as possible as we can.</p>
<h3 id="TODO"><a href="#TODO" class="headerlink" title="TODO"></a>TODO</h3><ol>
<li>Is each system call have fixed time?(ofcourse, there should be a litter<br>different for each testing)</li>
<li>Sort the time elapse for all the system call</li>
</ol>
<h3 id="Reference"><a href="#Reference" class="headerlink" title="Reference"></a>Reference</h3>
      
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